The objective of this proposal is to elucidate the proximate and ultimate carcinogens formed metabolically from the environmental polyaromatic hydrocarbons, 2- and 3-methylfluoranthene, benzo(b) bluoranthene, benzo(j)-fluoranthene, dibenxo(a,h) pyrene, dibenzo(a,i) pyrene, and dibenzo(c,g) carbazole. All of these environmental agents are carcinogenic on mouse skin or in the hamster respiratory system. Their presence in cigarette smoke, air pollution, coal tar, surface water, and soil is of particular concern because of actual human exposure. Although the environmental concentration of some of these carcinogenic agents exceeds that of benzo(a) pyrene, no studies have been reported on their metabolism. The methods proposed for the isolation and structural elucidation of the proximate carcinogens employ a combination of high pressure liquid chromatography and mutagenesis assay in S. typhimurium with suspect isolates being subsequently assayed on mouse skin. Structural elucidation of the isolated proximate carcinogens will be confirmed by unequivocal synthesis. Ultimate carcinogens will be synthesized from the proximate forms and assayed in newborn mice. Studies on the effect of representative environmental modifiers on the metabolic formation of the identified proximate carcinogen will then be performed. This is particularly important since man is exposed to these agents in mixtures of environmental pollutants.